Method of manufacturing a liquid crystal display panel

Abstract: In regard to a panel (1) in which a short-circuit ring (8) is formed of Al or an Al alloy of a gate wiring line or a source wiring line, the present invention is related to a method for removing the short-circuit ring after a process of inspecting defects of the panel, and provides a method for manufacturing a liquid crystal display panel by cutting a glass substrate outside the short-circuit ring made of Al, and thereafter removing the short-circuit ring by grinding the short-circuit ring while spraying on the substrate a water having a low resistance including something like carbon dioxide gas. According to the manufacturing method, since the low-resistance material of Al of the gate wiring line can be used as the short-circuit ring as it is, the material of Al can be commonly used as a current supply wiring line (6) in subjecting the material of Al to an anodic oxidation process. Therefore, it is not required to form a film of any metal other than Al and pattern the same, which can simplify or reduce the number of processes. Furthermore, since the material of Al is trimmed off by grinding, the Al material is not clawed in cutting the material of Al, which allows the cutting to be achieved without causing any short circuit between adjacent wiring lines nor slipping the tooth in scribing a scratch marking line by means of a scriber.

Description: The present invention relates to a method for separating a short-circuit ring which connects gate wiring lines or drain wiring lines of an array substrate in a manufacturing process of forming a liquid crystal display TFT array substrate into a panel. A liquid crystal display has been regarded as a very important display device for use in an information terminal of office automation, and accordingly there has been a rapid promotion of developing high-definition large-size liquid crystal display screens on the order of ten inches. Under the above-mentioned circumstances, there has been taken a lot of efforts in producing defect-free liquid crystal display panels employing active elements, in particular, a thin film transistor (referred to as a TFT hereinafter). However, since the TFT element is a field-effect transistor, a defective TFT is possibly produced due to electrostatic charges generated in the manufacturing process. Therefore, sufficient care or consideration is required. For the above-mentioned reasons, a short-circuit ring made of a Cr material, a Ta material, or an ITO material has been formed around the TFT array substrate, and after filling liquid crystals for the formation of a display panel, the above-mentioned short-circuit ring has been removed (Japanese Patent Laid-Open Publication No. SHO 63-180935). In a removing process, a scratch marking line is formed on a glass substrate by means of a scriber or the like, and thereafter the short-circuit ring has been separated by cutting. Since the aforementioned Cr material, Ta material, and ITO material are hard materials, they can be easily cut off. In more detail, when the gate wiring line or a source and drain wiring lines are made of a soft material such as Al, only the material of the short-circuit ring formed in the peripheral portion is changed into a material such as Cr so that the short-circuit ring can be easily cut off. However, in the current situation that large-size TFT array panels are produced, the gate scanning electrode is required to have a reduced resistance, and therefore a material including Al has been increasingly used as a gate wiring metal. In order to reduce the defect, there has been put in practice a system for forming an insulating film by subjecting the gate electrode made of Al, Ta, or the like to an anodic oxidation process. It is to be noted that only the short-circuit ring is formed of a material of Cr, Ta, or the like different from the material of Al. Thus, when the short-circuit ring is formed of a material different from the Al based material used for the gate wiring line or the source and drain wiring lines, a process of forming the different material and a patterning process therefor are further required. When the short-circuit ring is formed of the same material of Al as that used for the gate or source and drain wiring lines and the cutting is effected at a wire lead portion inside the short-circuit ring by dicing or similar means, since the wiring material of Al is soft, the material of Al is clawed to possibly cause short circuit between adjacent wiring lines. Furthermore, when the tooth of the dicing is made to run on the wiring line made of Al, the tooth tends to slip, resulting in a difficult cutting operation. Further prior art is known from the following documents: JP-A-63208023 relates to a production of a liquid crystal display element including a step of cutting a connection of a source line to an aluminum ring by laser scribing. JP-A-02190820 relates to a manufacture of a liquid display device including the steps of providing double short rings, removing the outer short ring by cutting the substrate near the inside short ring and removing the inside short ring by grinding a corner part of the cut substrate. JP-A-61296330 also relates to the manufacture of a liquid crystal display element including the step of polishing away of common electrodes provided on a substrate flank. SUMMARY OF THE INVENTION In order to solve the aforementioned problems, it is an object of the present invention to provide a method for easily removing a short-circuit ring made of Al after forming a liquid crystal display panel, preventing damage to the devices provided on the substrate. The present invention solves this object by a method having the steps as defined in claim 1. The invention takes the measures of preparatorily cutting a glass substrate in a portion where no wiring line exists outside the short-circuit ring made of Al by the dicing or a similar means, and thereafter trimming off the short-circuit ring in a grinding stage of a glass chamfering process. By taking the above-mentioned measures, even the soft wiring material of Al can be easily removed. By introducing the above-mentioned processes, the present invention is capable of easily removing the short-circuit ring made of Al of the TFT array substrate. The above-mentioned arrangement produces the advantages of causing no short circuit between adjacent wiring lines made of Al by the dicing and reducing the number of processes in comparison with the conventional case. Furthermore, by virtue of an advantage that the material of Al used for the gate or source and drain wiring lines can be utilized as a short-circuit ring as it is, there is no need to provide the processes of forming a film of another metal material and patterning the same. With the above-mentioned arrangement, the processes can be simplified or reduced, and when small-size TFT array substrates are segmented from a large-size TFT array substrate, the short-circuit ring made of Al can be fully utilized merely through the conventional processes. Furthermore, when the gate electrode made of Al is subjected to an anodic oxidation process, there is an advantage that a wiring line provided as a power supply line for the anodic oxidation process can be utilized as a short-circuit ring as it is. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view of an embodiment of the present invention, in which an anodic oxidation process is performed by commonly using a gate wiring material of Al and an anodic oxidation power supply wiring material of Al; Figs. 2 (a) and 2 (b) are simplified explanatory views of processes of removing a short-circuit ring made of Al on a TFT array of the embodiment of the present invention; and Fig. 3 is a graph showing a volt-ampere characteristic of the anodic oxidation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail with reference to the accompanying drawings. Referring to Figs. 1, 2 (a), and 2 (b), there are shown a TFT array substrate 1, a gate wiring line 2, an opposite substrate 3 of a liquid crystal display panel, a source wiring line 4, an anodic oxidation solution 5, a current supply wiring line 6 formed on the array substrate for forming an anodic oxidation film, a center line 7 of cutting by means of a dicing or a scriber, a short-circuit ring Al wiring line 8, an anodic oxidation current supply clip 11, a grinder 12, an anodic oxidation opposite substrate 13, an anodic oxidation constant current source 14, and water 15 having a low resistance. Referring to Fig. 1, a TFT array substrate on which the gate wiring line and the anodic oxidation current supply wiring line 6 are formed of Al or a material including Al are immersed in the anodic oxidation solution 5 to be subjected to an anodic oxidation process. The anodic oxidation process is performed under volt-ampere characteristic conditions as shown in Fig. 3. In the case of the material of Al, the anodic oxidation solution 5 is implemented by tartaric acid or citric acid. When growing an anodic oxidation film by 2000 Å, a voltage of about 100 V is applied. The application of the voltage is performed by using the current supply material of Al as the short-circuit ring 8, while the gate wiring lines 2 or the source wiring lines 4 are mutually connected in a manner as shown in Figs. 2 (a) and 2 (b). When the short-circuit ring is made to concurrently serve as an electrode for inspecting the display, the short-circuit ring for the source wiring lines 4 and the short-circuit ring for the gate wiring lines 2 are separated to be able to independently supply signals. The electrode substrate 13 that the clip 11 grips is to be removed by etching or in a similar manner in an array forming process after the anodic oxidation process is completed. Therefore, after the panel filled with the liquid crystals is completed, the short-circuit ring remains in the peripheral portion. In regard to the image display of the liquid crystal display panel, when the short-circuit ring of the gate wiring line and the short-circuit ring of the source wiring line are separated from each other, an inspection of defects is performed by inputting a signal to each of the short-circuit rings to effect a simultaneous image display on the entire panel screen. Subsequently, the substrate is subjected to a short-circuit ring removing process. According to the conventional system, it is required to scribe a scratch marking line inside the gate wiring line 2 and the source wiring line 4 and cut off the same. In such a case, since a wiring line made of Al is employed, when the scratch marking line is scribed at the wire lead portion made of Al, the material of Al is clawed to possibly cause short circuit between adjacent wiring lines. Therefore, according to the present invention, only the glass substrate is firstly cut off outside the short-circuit ring formed of the wiring line made of Al. In the above stage, a distance between the center of the dicing tooth or the center line 7 along which the glass substrate is to be cut by means of a diamond cutter 9 of the scriber and the outer end of the short-circuit ring is designed to be greater than a half of the thickness of the dicing teeth. The above-mentioned arrangement is to prevent the short-circuit ring from being scratched in the scratch marking line scribing process by means of the scriber. Since the thickness of the dicing teeth is normally about 200 µm, the center line 7 is designed to be separated by 100 µm apart from the end of the short-circuit ring made of Al . Furthermore, since the chamfering of the glass substrate in a subsequent process is about 200 µm to 500 µm, the width of the short-circuit ring is designed so that the distance between the center line 7 of cutting and the inner end of the short-circuit ring is 500 µm. When removing the short-circuit ring made of Al from the liquid crystal display panel having the TFT array substrate designed as described above, firstly the glass substrate is cut to have a specified size by the dicing. Otherwise, it is acceptable to scribe a scratch marking line by means of the scriber and thereafter cut the glass substrate by striking the substrate end. In the above-mentioned stage, electrostatic charges tend to take place because the glass substrate is rubbed in the process of dicing. Therefore, the cutting or the scribing of the scratch marking line is performed by spraying on the substrate a water having a low resistance including CO 2 . According to an experiment, a dielectric breakdown of the TFT array has occurred without spraying on the substrate the water having a low resistance, and it is also confirmed that such a trouble can be avoided by spraying the water on the substrate. Then, as shown in Fig. 2 (b), the edge portion of the glass substrate cut in the grinding process is then chamfered. In the above stage, the short-circuit ring is ground off simultaneously with the chamfering. In performing the chamfering process, the grinding is also effected while spraying on the substrate the water having a low resistance in order to prevent the electrostatic charges from taking place. By removing the short-circuit ring of the array designed as described above through the aforementioned processes, even in the case of an array substrate employing a short-circuit ring made of Al or an Al alloy, the removal of the short-circuit ring can be easily achieved.

Claims: A method for manufacturing a liquid crystal display panel, having a liquid crystal display thin film transistor array made on a glass substrate, comprising the steps of: preparing a short-circuit ring (8) for connecting gate wiring lines (2) or drain wiring lines and made of a material including aluminum, prior to rubbing the substrate for alignment of a liquid crystal material; filling the panel with said liquid crystal material; and removing said short-circuit ring (8), wherein said step of removing includes cutting the glass substrate adjacent to the short-circuit ring and removing the short-circuit ring by grinding an edge portion of the glass substrate obtained by the cutting step, characterized in that said step of removing the short-circuit ring by grinding the short-circuit ring is performed while spraying on the substrate a water (15) including CO 2 and having a low electrical resistance. A method for manufacturing a liquid crystal display panel according to claim 1, wherein a distance between the outer end of the short-circuit ring (8) and a center of the cutting (7) of the glass substrate is greater than a half of a thickness of a tooth for cutting the substrate. A method for manufacturing a liquid crystal display panel as claimed in claim 2, wherein a distance between a center of the cutting (7) of the substrate and an inner edge of the short-circuit ring is designed to be within 500 micrometers. A method for manufacturing a liquid crystal display panel according to claim 1, wherein the short-circuit ring (8) and a current supply wiring line (6) for subjecting the gate wiring line (2) to an anodic oxidation process are electrically connected to one another.

Inventors: KOBAYASHI IKUNORI, TAKEDA MAMORU, UNO MITSUHIRO, KOBAYASHI, IKUNORI, TAKEDA, MAMORU, UNO, MITSUHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: G02F1
IPC codes: H01L21, H01L29, G02F1